My name is Adam Blackwood, Head Brewer at Speyside Craft Brewery. I am originally from Cape Cod, Massachusetts USA. I took my undergraduate at University of Edinburgh and my masters in Brewing and Distilling at Heriot-Watt University in the same great city. I was a homebrewer for a few years before and during that.
Mash efficiency. I know this is a subject close to all brewer’s hearts, so it is worth a quick look at exactly what that means.
Extract is based on the malt, and the maltster provides the analysis of their grain. In the UK the measurement is based one litre of wort at S.G. 1.001. one kilogram of a malt at 20 °C will give its potential extract, and list it as hot water extract, or L°/kg. Therefore in order to know how many kgs of a particular malt that is being used would be calculated as:
I find it easiest to use a spreadsheet to manipulate the formulas; that way you can set the volume and specific gravity and have it calculate the extract needed. It also tells me how many kgs I need to start with.
Efficiency can be measured at a couple of points in the process. The most true sense is the pre-boil gravity. This is in the kettle when there will be a known volume and gravity. However, wort doesn’t necessarily mix well and it can be hard to get an accurate figure here. On a small scale mixing shouldn’t be a big problem, but be careful to not make too much foam as this will be lost later in the process - extra oxygen at this stage does not help. I measure efficiency into the fermenter. You must also consider volume losses in pipes, and hop loss, particularly with whole leaf hops and the difference between varying levels of hops. I lose a lot less in the stout versus the IPAs.
One of the easiest ways to improve your mash efficiency is to thin your liquor-to-grist ratio. I find although your parameters should include a liquor-to-grist ratio, it usually dictated by the parameters of a brew kit than a particular recipe. When I first started it was definitely at the low end, fluctuating between 2-2.4 L/kg. As we have a single infusion mash and our liquor doesn't mix well with the grain going in, most mixing is manual. This made it incredibly difficult to mix it in. I also found this leads to a very thick grain bed during run off, leading to a really slow sparge.
I have since moved the liquor-to-grist ratio up to 2.8 L/kg. I still get very strong first worts and unless going for a very big beer -say 8% or more -, this shouldn't be a problem. In terms of denaturing your enzymes, a thicker mash does help enzymes last longer in a thicker mash, but also allows for ease of movement; enzymes can break down further in a thinner mash. We usually mash warmer, 66C or 67C depending on the beer. I find my attenuation is still very good, in line with having a bit higher final gravity for some more residual sweetness, but still usually about 80% attenuation with a slightly thinner mash.
Getting a better mix as the mash tun is filled increases your efficiency. This really helps to reduce clumps. I also have found that increasing the bed of liquor over the plate is advantageous.
A longer, more consistent sparge helped increase efficiency. I increased the sparge from about 45 minutes to an hour and a half. Although conversion should end quickly in the mash, I find this helps the solubility of the sugars leading to more in the kettle and less going to waste. Imagine the sparge water slowly creating gaps in the bed where more sparge water can get through, avoiding areas that potentially still have extract. If the sparge is more consistent the grain bed settles better, and the level in the mash tun can slowly decrease while still maintaining a layer of water above the bed. If I need to momentarily cut sparge going in to match run off better, this is when I have the worst bed stability, leading to a mash that could be more mix with your last runnings and become waste. Although there is some research on last runnings extracting tannins, I find even if I run below the grain bed at the end of the sparge I can’t pick up on tannin flavours.
One study found that increasing the temperature of the mash to 95C and then sparging with 77C water decreased mash efficiency, showing that at cooler temperatures conversion continues. The reason they did this was to test if they could sparge quicker. Although for some a shorter brew length means more brews a day, on our setup we can do two brews a day and I see no advantage in losing efficiency for speed.
Many people will discuss the crush of the grain as significant for efficiency. I must admit it’s not something I have too much control over as I buy my grain crushed. I will say it is at least consistent, as my efficiencies batch to batch aren't more than a couple of percent out. As an interesting aside, a mash filter gets over 100% efficiency as the hammer milling causes better extract than the lab test. It is also worth noting the official EBC test has a very thin mash.
Our pH in mashes doesn't seem to have any real noticeable impact. Granted the only beers that have different pHs from the rest of the core range are the lager (which we don't use any brewing salts) and the stout. The stout gets the worst efficiency, but this might have to do with the lower diastic power as the pale percentage of the grain bill is relatively low.
There should be some useful downloads that will help you with increasing your mash efficiency. More with each blog